Microwave transmission lines



April 28, 1959 Y J. A. KOSTR!ZA ETAL MICROWLAVE TRANSMISSION LINES Original Filed Feb. 2. 1953 .fl iql 1). L.

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A ttorn e y April 28, 1959 J. A. KOSTRIZA ET AL J MICROWAVE TRANSMISSION LINES Original Filed Feb. 2, 1953 2 Sheets-Sheef. 2

. I i//////////4I Inventors JOHN A. kOSrR/ZA -PA u TERRA/V0 VA A Home y MICROWAVE TRANSMISSION LINES Original application February z, 1953, Serial No. 334,486. Divided and this application August 20, 1958, Serial No. 756,246

11 Claims. crass-9 This invention relates to power splitting junctions and more particularly to transducer junction arrangements for splitting microwave energy between two dififerent types of waveguides. This is a division of our copending application, Serial No. 334,486, filed February 2,, 1953.

In thecopending applications of D. D. Grieg and H. F. Engelmann, Serial No. 234,502, filed June 30, 1951, now Patent No. 2,721,312, and M. Arditi and P. Parzen, Serial No. 286,764, filed May 8, 1942, now Patent No. 2,774,046, microwave waveguides comprising generally a line'abovegroun type of transmission line, over which microwave energy may be propagated in a mode simulating a TEM mode are shown. In this type of transmission line, a planar conductor is employed as a ground conductor with a line conductor disposed in spaced parallel relation thereto by means of a strip or layer of dielectric material.

Patented Apr. 28, v1959 2 l r I splitting junction according to the principles of this inven tion, the sectional view being taken along line 1-1 of Fig. 2; s v

Fig. 2 is a sectional view showing the line-'above-ground waveguide of Fig. 1 in plan view, the section beingtaken along line 2-2 of Fig. 1;

Fig. 3 is a cross-sectional view taken along lines .3-3 of Figs. 1 and 2;

Fig. 4 is a longitudinal sectional view of another power splitting transducer junction according to this invention, the view being taken along line 4-4 of Fig. 5;

Fig. 5 is a sectional view taken along line ,5-5 of Fig.4; v 1

Figs. 6 and 7 show a further embodiment of the invention, Fig. 6 being a longitudinal sectional view taken along line 6-6 of Fig. 7, and Fig. 7 being a cross- The line and planar conductors are preferably of dif- I ferent widths; that is, the planar conductor is made wider than the line conductor so that it appears as an infinite conducting surface to the line conductor, thereby insuring an electric field distribution characterized generally by the TEM mode. For example, the field distribution is believed to be similar to that which occurs between one of the conductors of a truly parallel conductor system and the neutral plane between such conductors. The important parameters of this type of transmission line are thevwidth of the line conductor and the dielectric spacing between the line conductor and the planar conductor.

' One of the objects of this invention is to provide power splitting transducer junctions for splitting microwave energy between branch Waveguides wherein one or more of the branches comprises a line-above-ground type of waveguide.

Another object is to provide a transducer arrangement to effect energy coupling between a line-above-ground type of waveguide and another type of waveguide or cavity resonator.

One of the features of this invention is the provision of a line-above-ground type of waveguide in coupling relation to another type of waveguide such as the rectangular waveguide or coaxial waveguide or with a cavity resonator. The line-'above-ground type of waveguide is employed as two branches in coupled relation to a different type of waveguide or resonator and is provided with transducer structures for effecting transfer of microwave energy between the line-above-ground type of waveguide and the other type of waveguide or resonator. The transducer structures may comprise various conductor shapes 'associated with the line conductor of the line-above-ground waveguide including conductor portions in the plane of the line conductor or in the form of posts or vanes at an angle to the plane of the line conductor.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent by reference to the following de scription taken in conjunction with the accompanying drawings, wherein:

Fig. 1 is a longitudinal sectional view of an energy sectional view taken along line 7-7 of Fig. 6;

Figs. 8 and 9 are views of still another embodiment of an energy splitting transducer, Fig. 8 being taken along line 8-8 of Fig. 9 and Fig. 9 being taken along line 9-9 of Fig. 8.

Referring to Figs. 1, 2 and 3 of the drawings, the lineabove-ground type of waveguide is shown to comprise a first conductor 1, a second conductor 2 spaced apart by a thin strip or layer of dielectric material 3. The two conductors 1 and 2 are preferably of flat strip form, the first conductor being wider than the second conductor so that propagation of microwave energy therealong is in an approximate TEM mode as hereinbefore explained. The dielectric material may be polyethylene, polystyrene, Teflon, fiberglass or laminated fiberglass impregnated with Teflon, quartz, or other suitable material of high dielectric quality. The conductors 1 and 2 are preferably formed on the dielectric strip by any of the known printed circuit techniques, the one preferred being an electrolytic etching process.

As shown more clearly in Fig. 1, the junction comprises three branches 4, 5 and 6. The branches 5 and 6 comprise the line-above-ground type of waveguide, the two branches being interconnected so that the second con ductor 2 thereof comprises a continuous line. The branch 4 in this embodiment comprises a rectangular waveguide, the terminating end of which is provided with an adjustable short 7 rearwardly of the conductor 2 of branches 5 and 6. The two opposed walls 8 and 9 of the rectangular waveguide are provided with aligned openings 10 and 11 through which the conductor 2 of the branches 5 and 6 extend. The conductors 1 of the two branches 5 and 6 are terminated at the Walls 8 'and9 to which they are electrically connected.

To enhance wave energy coupling between the branches, the second conductor 2 is provided with laterally extended portions 12 and 13 partly disposed within the hollow structure of the rectangular waveguide. Theselateral extensions are preferably integral with the conductor 2 and are carried by the dielectric strip 3 in the plane of the conductor 2. While the shaping of these laterally ex tended portions may follow various forms, one preferred form is provided with a taper, as indicated at 12a in the direction of the slots longitudinally of the conductor 2.

g The slots 10 and 11, as more clearly shown in Fig. 3,

' are of such size as to provide proper dielectric spacing with respect to the conductor 2, one side of the slot being enlarged as indicated at 11a so that the wall containing the slot does not interfere with the electrical lines of force between the conductors 1 and 2.

Assuming a source of microwave energy connected to the branch 4, the wave energy propagated along branch 4, as indicated at 14, is split substantially equally between the branches 5 and 6, as indicated at 15 and 16. By properly adjusting the short 7, an impedance match be tween the branches is readily obtainable. Assuming that the source of wave energy is coupled to branch 5, the I propagation therealong is split between branches 4 and 6, the division ratio being dependent upon the size and location of the transducer sections 12 and 13. If desired, section '13 may be omitted-when the power source is -cou pled-to branch 5, and when coupled tobranch 6, the section 12 may be omitted.

Referring :to Figs. 4 and 5, another embodiment of the invention is shown wherein the transducer arrangement differs from that shown in Figs. 1 to 3 and wherein the first conductor 1 of branches and'6 forms the end termination of the rectangular waveguide of branch 4. The first conductor 1 is electrically connected to the fourwalls of --the waveguide forming branch 4, thus establishing a terminating wall '1a or the branch 4. The transducer structure includes 'two lateral extensions 17 and 18 which lie in the plane of the conductor 2 and are contained within the rectangular waveguide. These two sections 17 and 18 taken togetherforirr-substantially an elliptical area. The sections 17 and 18 may be triangular but preferably the sides thereof are curved substantially as indicated in Fig. '5. The transducer includes a third-vane-like section '19 disposed at right angles to the plane ofthe conductor 2 and extends longitudinally of the rectangular waveguide of branch 4. This section 19 is shown to taper in the direction of the branch -4 so as to provide a gradual transition from the conductor 2 into thepassage of the waveguide. In the form illustrated in Figs. 4 and 5, power propagated along branch 4 is equally divided between the branches 5 and 6. Likewise, power propagated along one of-the branches such as branch 5, for example, may be equally divided or divided according to a desired ratio between 'the'branches 4 and 6 dependentupon the structural proportions of the transducer.

Figs. 6 and'7 show ajunction similar to that shown in Figs. 4 and 5 except that the transducer is different. In this embodiment the transducer is made up as a separate unitwhich-is soldered or otherwise secured in place on the conductor 2 of branches 5 and 6, the transducer having a base composed of two identical sections 20 and 21 and a third vane-like section 22 disposed at right angles thereto. This transducer is particularly constructed to divide equally the wave energy propagated along branch '5 between the branches 4 and 6. The front portions of the sections 20 and 21 are curved as indicated at 23, and thefront edge of the vane section 22 is inclined so as to provide improved transition from the line-above-ground waveguide to the rectangular waveguide. For energy propagated over branch 6, the ratio of division is such that ;a smaller portion of power is diverted over branch 4-than in the case where the source of energy is applied tobranch-S. By making transducer sections symmetrical substantially as illustrated in 'Figs. 4 and 5, with proper dimensions, an equal division may be'had regardless which branch is connected to the source of power. While sections 20' and 21 are shown separate from conductor :2, it should be understood that they may be made integral therewith and in the same plane. It will also be understood that the transducers of Figs. 1-3 and 4-5 may be made separate from conductor 2'if desired.

Referring to Figs. 8 and 9, still another embodiment of the invention is shown wherein the difference from the embodiment shown in Figs. 1 to 3 is also in the transducer structure. In this form the transducer comprises two cross-conductors disposed diagonally crosswise of the rectangular waveguideof branch 4 as indicated at 25 and 26. The ends ofthe conductors'25 and 26 may beelectrically connected to the walls of the waveguide and disposed in contact, or integral if desired, with the conductor 2 of branches 5 and 6. The transducer arrangement of conductors 2.5 and 26 provides for equal division of energy regardless to which branchthe sourceis applied. To further enhance thisdivision, the transducer-may include a conductive probe 27 disposed axially of the waveguide br ch?!- While we have described above the principles of our invention in connection with specific apparatus, :it is .to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.

We claim:

1. A waveguide junction having three branches, at least one of said branches consisting of a hollow structureand the other of said branches consisting of a type of .waveguide which comprises a first conductor, a second conductor and means to maintain said conductors in dielectrically spaced substantially parallel relation, said first conductor being wider than :said second conductor so (that said first conductor presents substantially a'planarsurface with respect to said second conductor, said hollow structure comprising a rectangular waveguide two opposed walls of which have aligned slots and both of the other of said branches comprise said waveguide type wherein the .secondconductors of the two branches are interconnected and extend in dielectric spaced relation through said slots with the firstconductors of said two branches connected to the walls of said rectangular waveguide, and a transducer carried by said second conductor with at least a part thereof disposed within said hollow structure to enhance the coupling of wave energy from one to the-other of said branches.

2. A waveguide junction according to claim .1,-wherein said transducer includes conductor portions certain of which are disposed inthe plane of said second conductor and other of which is disposed longitudinally of saidrectangularwaveguide.

3. A waveguide junction having three branches, at least one of said branches consisting of a hollow structure and the other of said branches consisting of a type of waveguide which comprises a first conductor, a second conductor and means to maintm'n said conductors in dielectrically spaced substantially parallel relation, said first conductor being wider than said second conductor so that said first conductor presents substantially a planar surface with respect to said second conductor, said hollow structure comprising a rectangular waveguide two opposed walls of which have aligned slots and both of the other of said branches comprise said waveguide type wherein the second conductors of the two branches are interconnected and extend in dielectric spaced relation through said slots with the first conductors of said two branches connected to the walls of said rectangular waveguide, said rectangular waveguide being provided with a terminating short rearwardly of said slots, and a transducer carried by said second conductor with at least a part thereof disposed within said hollow structure to enhance the coupling of wave energy from one to the other of said branches.

4. A waveguide junction according to claim 3,wherein said terminating short comprises said first conductor disposed as the end wall of said waveguide.

5. A waveguide junction according to claim 3, wherein said terminating short comprises a shorting device adjustable relative to the junction of said rectangular waveguide and the other two branches.

6. A waveguide junction having three branches, at least one of said branches consisting of a hollow structure and the other of said branches consisting of a type of waveguide which comprises a first conductor, a second conductor and means to maintain said conductors in dielectrically spaced substantially parallel relation, said first conductor being wider than said second conductor so that said first conductor presents substantially a planar surface with respect to said second conductor, said hollow structure comprising a rectangular waveguide two opposed walls vof which have aligned slots and bothof the other Off said branches comprise said waveguide type wherein the secondconductqrs of the twobranches are interconnected and extend in dielectric spaced relation through said slots with t t e wad agr .Qf s id We ran h c nec d to the walls of said rectangular waveguide, and a transducer carried by said second conductor with at least a part thereof disposed within said hollow structure to enhance the coupling of wave energy from one to the other of said branches, said transducer including a conductor portion disposed laterally of said second conductor.

7. A waveguide junction according to claim 6, wherein the conductor portion of said transducer is integral with said second conductor and disposed in the plane of said second conductor. a

8. A waveguide junction according to claim 6, wherein said conductor portion is tapered in at least one direction longitudinally of said second conductor.

9. A waveguide junction according to claim 6, wherein said conductor portion includes two tapered sections disposed at least partly within said hollow waveguide with the taper thereof in the direction of said slots.

10. A waveguide junction according to claim 6, wherein the conductor portion of said transducer is disposed longitudinally of said rectangular Waveguide.

11. A waveguide junction according to claim 10, wherein said conductor portion is tapered in a direction away 10 from said second conductor.

No references cited. 

